The aerodigestive system is comprised of a complex of integrated anatomic structures that support both ingestive and respiratory physiologies throughout the human lifespan. The developmental origins of this system---in both its form and function, begin in utero where prenatal morphologies and associated processes form the foundations for extrauterine survival at birth. When this prenatal development is disrupted, alterations to normal physiologic functioning may serve as antecedents of later neonatal respiratory distress, dysphagia, or upper gastrointestinal dysfunction. Further, premature birth before upper airway processes are fully established may exacerbate many of these conditions. In turn, this may prompt a cascade of respiratory-related dysfunctions throughout postnatal life. It is therefore important to understand how the respiratory system develops, how mechanisms regulate normal emerging physiologic processes, and the events that predicate fetal and neonatal compromise. To do this work in the living human fetus, we apply a novel noninvasive ultrasound imaging and analysis method to measure the role of altered amniotic fluid exchange in developing prenatal respiratory and ingestive mechanisms. The key components of this protocol are to: 1. Extend the use of prenatal ultrasound sonography to detect and measure the developing upper aerodigestive region. 2. Prospectively characterize differences in ingestive versus respiratory fluid flow-related dynamics across maturation in normal fetuses and those with conditions that may influence airway development. Using spectral Doppler-derived fluid flow analyses, we will map across the spectrum of gestation the fluid dynamics of upper airway development and the factors that influence functional integrity of upper airway amniotic fluid exchange. 3. Identify how deviations in amniotic fluid regulation within the upper aerodigestive system may be associated with fetal and neonatal morbidity and mortality and, the predictive utility of these indices in conditions such as oligohydramnios or polyhydramnios. This study (approved by NIH IRB on August 5, 2003; NNMC IRB pending October 9, 2003) is a collaborative effort with National Naval Medical Center Bethesda, Childrens and Womens Health. The project uses a novel standardized 4-axis sonographic examination to quantify growth and respiratory-related fluid flow mechanics in the upper airway of the living human fetus. The use of this noninvasive ultrasound technique as part of the clinical prenatal examination will not only discriminate function at four upper airway sites (perinasal, oral, pharyngeal, and tracheal), but provide estimates of amniotic fluid flow volumes, inspiratory-expiratory fluid flow velocities and durations, and Doppler waveform patterns associated with fetal breathing and ingestive processes. This provides a method to explore how deviations in amniotic fluid regulation may be associated with morbidity and mortality and, the predictive utility of these indices in understanding conditions such as oligohydramnios or polyhydramnios. The germinal database will include healthy fetuses 16.0 to 39.6 weeks gestational age and test cases with polyhydramnios/oligohydramnios. By elucidating how developing structures integrate with emerging upper respiratory behaviors, this work will document the maturational events underlying normal function at birth that in turn may facilitate future clinical strategies for successful postnatal care.